A software architecture for autonomous orbital robotics

SUMO, the Spacecraft for the Universal Modification of Orbits, is a DARPA-sponsored spacecraft designed to provide orbital repositioning services to geosynchronous satellites. Such services may be needed to facilitate changing the geostationary slot of a satellite, to allow a satellite to be used until the propellant is expended instead of reserving propellant for a retirement burn, or to rescue a satellite stranded in geosynchronous transfer orbit due to a launch failure. Notably, SUMO is being designed to be compatible with the current geosynchronous satellite catalog, which implies that it does not require the customer spacecraft to have special docking fixtures, optical guides, or cooperative communications or pose sensors. In addition, the final approach and grapple will be performed autonomously. SUMO is being designed and built by the Naval Center for Space Technology, a division of the U.S. Naval Research Laboratory in Washington, DC. The nature of the SUMO concept mission leads to significant challenges in onboard spacecraft autonomy. Also, because research and development in machine vision, trajectory planning, and automation algorithms for SUMO is being pursued in parallel with flight software development, there are considerable challenges in prototyping and testing algorithms in situ and in transitioning these algorithms from laboratory form into software suitable for flight. This paper discusses these challenges, outlining the current SUMO design from the standpoint of flight algorithms and software. In particular, the design of the SUMO phase I laboratory demonstration software is described in detail. The proposed flight-like software architecture is also described.